Is viagra a good idea?

we have been married for 3 years. we want to start ttc,but my husband is tired all the time and doesnt feel like having sex except maybe on the weekends when he doesnt work. we does works alot, but idk what to do. we are thinking about viagra,but he doesnt want to go to the dr. is there something similar to viagra that we can get over the counter or internet? Thank you!